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The Incredible Regularity of Periodic Abrupt Climate Change
Rahmstorf, S.  2003.  Timing of abrupt climate change: A precise clock.  Geophysical Research Letters 30: 10.1029/2003GL017115.

What was done
The author analyzed the GISP2 ice core record from Greenland with respect to the timing of Dansgaard-Oeschger (DO) warm events.

What was learned
In the words of the author, these abrupt climate changes "appear to be paced by a 1,470-year cycle with a period that is probably stable to within a few percent."  With 95% confidence, for example, the period is maintained to better than 12% over at least 23 cycles during the time interval 51 to 10 thousand years BP.  In fact, Rahmstorf reports that "the five most recent events, arguably the best-dated ones, have a standard deviation of only 32 years (2%)."

What it means
Rahmstorf concludes, and rightly so, that this finding "strongly supports the idea that the events are paced by a regular 1,470 year cycle" and that "the highly precise clock points to an origin outside the Earth system."  He also notes "there is some evidence that this cycle may also be present in the Holocene but does not trigger DO events then, possibly because the Atlantic ocean circulation is not close to a threshold in a warm climate," suggesting further that "the so-called 'little ice age' of the 16th-18th century may be the most recent cold phase of this cycle."  Taken together, these observations suggest that the warming of the past century or so is likely nothing more than the logical next phase of this repeating pattern of cyclical warming and cooling that is paced by some highly regular extraterrestrial forcing factor.

Reviewed 3 September 2003